During the fabrication of a semiconductor package, a lead frame is electrically connected to a semiconductor die. The semiconductor die is mounted on a die attach pad (DAP) and electrical connections are made between the leads of the lead frame and the die. A plastic molding then encapsulates the die along with a portion of the metallic lead frame. An external portion of the lead frame remains outside the molding and provides a means for sending electrical signals to the die from outside of the package. The external portion of the lead frame may be connected to a printed circuit board (PCB). Typically the die attach pad is simply a segment of the lead frame, thus the die attach pad is mechanically connected to the lead frame because the two components are unitary. Electrical connections are provided by gold or aluminum wires that are wirebonded between the die and the leads of the lead frame. In certain “downset” packages, the die attach pad portion of the lead frame is “stamped” to depress the pad below the plane of the lead frame. Unfortunately, the stamping process necessitates using a package with a large footprint, as the footprint must accommodate the sloping downset that is produced during the stamping process. Even a small die will require a large package. The downset wastes space. An alternate method for fabricating a package uses a separate lead frame and die attach pad. Gold wires provide the electrical connection. The pad and the frame are mechanically attached with high temperature tape or solder. The high temperature used to activate the adhesive often precludes using die attach pads that contain delicate components, as such components may be thermally damaged when the frame is attached.
An alternative method for attaching a die to a lead frame is desired that allows pads with delicate components to be connected to the lead frame.
It is also desired to provide an attachment method that may easily be adapted to connect a variety of die attach pads with a variety of lead frames.
Further, a semiconductor package is desired that minimizes the size of the die footprint.